linux-kernel - Re: ipmi_si feature request: SMBIOS-based autoloading

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Message-id: <56A7757A.6040704@acm.org>
Date:	Tue, 26 Jan 2016 07:32:42 -0600
From:	Corey Minyard <minyard@....org>
To:	Andy Lutomirski <luto@...nel.org>,
	OpenIPMI Developers <openipmi-developer@...ts.sourceforge.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	brijeshkumar.singh@....com, Jean Delvare <jdelvare@...e.de>
Subject: Re: ipmi_si feature request: SMBIOS-based autoloading

On 01/24/2016 07:45 PM, Andy Lutomirski wrote:
> ipmi_si doesn't autoload on systems where it's found via SMBIOS.
> Could that be fixed?

I'm not really sure.  I kind of assumed this was handled in userland
like the ACPI tables.  I don't think there are many systems that have
SMBIOS and not ACPI, so I'm not sure of the impact here or what
to do.

> If I were doing it, I'd suggest rigging up some code that's compiled
> in to the main kernel even if ipmi_si is a module that creates the
> platform device if the dmi device is there and then set up a modalias
> so that the platofrm device causes ipmi_si to load.
>
> (In general, having the same driver create the platform device and
> register the platform driver means that autoloading is unlikely to
> work right.  See arch/x86/kernel/pmem.c for an example of a weird
> legacy device that gets this right.)

This sounds like kind of a hack.

> Alternatively, maybe /sys/firmware/dmi could learn how to advertise
> modaliases.  But that might be a giant mess to solve a tiny problem.

This sounds like the right way, but you are probably right.  Are
there any other resources that could benefit from this?  I"m
guessing not.

There is already a "dmi_save_ipmi_device" function that gets called
when scanning the SMBIOS table (see drivers/firmware/dmi_scan.c).
Maybe a tie-in there?  That happens pretty early, though, I'm not
sure if it's too early.

Of course it would be easy to have a file like pmem.c that detects
if an IPMI device is in the SMBIOS table and create a platform
device for it.

Are you willing to do this work?

-corey